Art of converting hydrocarbon oils



Dec. 18, 1934. J. K.'ROBERTS ART CONVERTING HYDROCARBON OILS Filed April 29, 1933 p X W F? 3 a a A m I 9 m |l||| w Tm E QM H ATTORNEY Patented 1 8, 1934 UNlTEDiSTATESj PATENT OFFICE ART OF CONVERTING 'HYDBOCARBON OILS Joseph K. Roberts, Hammond, Ind., assignor to Standard Oil Company (Indiana), Chicago, IlL,

a corporation of Indiana 1 Application April 29, 1933, Serial No. 668,524

2 Claims.

a maximum yield of a high anti-knock gasoline,

.without excessive carbon formation.

In accordance with my invention, a clean stock, such as a reflux condensate, produced in the operation, may be subjected to a high crack per pass to produce a gasoline of high anti-knock qualities. The vapors resulting from the high heat treatment may be separately digested or soaked at an elevated temperature and any liquid formed during the digestion or soaking operation removed at a rate adequate to prevent the accumulation of the liquid therein. The vapors resuiting-from the digestionor soaking operation may thereafter be subjected to fractionation to obtain a desired gasoline distillate therefrom. A second stream of oil,-in the nature of a dirtier stock, may beseparately heated to a light cracking temperature br a viscosity breaking temperature and further cracked or digested in the liquid phase in an enlarged zone. The vapors resulting from the liquid phase digestion of the dirtier stock may be commingled with the highly cracked vapors, together with unvaporized constituents I from the liquid phase treatment, and subjected to further digestion and scrubbing to obtain a vapor fraction of the desired endpoint which may be fractionated to obtain an exceptionally clean liquid fraction suitable for high cracking conditions and a vaporized constituent that may be condensed to recover a gasoline distillate of a high anti-knock rating.

In order to make my invention more clearly understood, I have shown in the accompanying drawing a diagrammatic elevational view of an apparatus suitable for carrying out my invention,

' the particular apparatus shown being merely for. thepurpose of carrying my invention into 'prac-' tical effect without limiting the improvements in theiruseful applications to the. particular construction, which, for the purpose'of explanation has been made the subject of illustration;

Referring to the drawing, I-have shown a furnace 1 having aconvection coil 2 and a radiant coil 3 positioned therein separated by a bridge wall. Any suitable bm'ner arrangement may be employed for imparting the necessary heat to both the radiant and the convection sections.

The numerals 4 and 5 represent reaction or digestion zones for soaking the vapors produced in the vapor phase treatment, The numeral 6 represents an enlarged chamberthat may be for the liquid phase soaking drum. The numeral '7 represents a chamber that may be employed as a combined evaporating and primary fractionating column. A suitable dephlegmating column, such as a conventional bubble tower, is in-- dicated at 8 .and a reflux condenser associated I with the bubble tower 8 isrepresented by the numeral 9. The numeral 11 represents a condenser and the numeral 12 a gasoline distillate receiver.

The enlarged vessels ,4, 5, 6, 7 and 8 may be of 10 the conventional type and suitably insulated against heat loss. v I

Fresh charge, in the nature of a dirty gas oilor a reduced crude may be forced through the line 13 by means of a pump 14-and passed through a coil 15 positioned in the reflux condenser 9. The fresh oil passing through the coil 15 may be preheated by indirect heat exchange with vapors passing through the reflux condenser 9. The preheated charge may then be passed through a line 16 through a suitable heat exchanger 17 where additional heat may be imparted thereto by indirect heat exchange with a portion of the reflu'x condensate, the formation of which will be hereinafter explained, from the bubble tower 8. The charge after receiving additional heat in the heat exchanger 17 may be passed through a line 18 to the convection coi 2 positioned in the convection zone of the furnace 1'. From the convection coil 2 the oiLmay be passed to another section of coil 19 connected to the convection coil 2 and positioned 1 against the bridge wall in the radiant section of the furnace 1. The oil passing through the convection section 2 and the radiant coil 19 may be heated to a light cracking temperature. In accordance with my invention the charge may rapidly be heated to a temperature at which carbon deposition may be substantially avoided in the convection coil 2 and the radiant coil 19.

The charge after being heated to .the desired temperature may be passed through-a transfer line 21 extending to the enlarged vessel 6. for example to the upper portion thereof, wherein a la e body of oil maybe subjected to cracking. Super-atmospheric pressurej may be maintained on thecharge passing through the heating coils and in the enlarged chamber 6. The charge en-; tering the enlarged chamber 6 may be substantially in liquid phase or in mixed vapor-liquid phase, and the vapors separated therefrom in may be commingled with the vapors passing through the line 22 in a manifold line 24 enterpors and liquid constituents introduced into the chamber 7 may be further digested and the resulting vapors together with highly cracked vapors as will be later explained pass upwardly through the enlargedchamber '7 whereinthey may be fractionated. As indicated in the drawing suitable trays may be provided in the enlarged chamber '7 for aiding fractionation.

In trder to fractionate the upwardly rising vaporous constituents to the desired end point, a portion of the reflux condensate formed in the lower part of the bubble tower 8, as will be hereinafter explained, may be withdrawn by means of a pump 25 and forced through the line 26 into the heat exchanger 1'7 where the reflux condensate may be partially cooled by the indirect contact with the fresh charge passing therethrough. The portion of the reflux condensate which was withdrawn may be further cooled by passing it through a second heat exchanger 27 wherein the reflux condensate may be brought into heat exchange with a suitable cooling fluid, such as water or"oil. tion of the reflux condensate to be used as a refluxing medium may be passed through" the line 28 into the enlarged chamber '7 by means of a valved-line 29. The upwardly rising vaporous constituents produced as before described, to-- gether with the highly cracked vapors pass around the trays inthe enlarged chamber 7 and are contacted by the downwardly flowing refluxing medium introduced through the line 29. The vapors resulting from the primary fractionating 1 operation which may be-of the desired end point,

may be passed through a vapor line 31 into the lower portion of thebubble tower 8. If the teinperature in the chambers 4 and is too high,

' a portion of the cooled reflux may be introduced thereinto by means of a line 30' for the purpose of preventing coke deposition. Unvaporized con-.

stituents in the nature of light tar may be passed through the line 30 toa tar stripping plant. The vapors passing through the bubble tower 8 may be further rractionated therein in order to remove heavy constituents therefrom and-may be passed through the reflux condenser 9 where additional heavierconstituents may be removed. The vaporous constituents of the desired end point may be passedthrough' a line 32 from the reflux condenser 9 to the condenser 11 wherein they are condensed. The liquid constituents may then be passed through a line 33 to the gasoline" distillate receiver 12 which may be provided with a valved gas outlet 34 and agasoline distillate valved drawoff 35.

a The heavier constituents removed from the:

. vapors passing through, the bubble .tower 8 may be collected as liquid in the bottom thereof and may, in operating in'accordance with my invention, be an exceptionally clean stock of the desired color and end point. The liquid constituents in the nature of reflux condensate may be subjected to a high crack per pass under vapor phase cracking conditions. The reflux condensate may be withdrawn from the lower portion of the bubble tower 8 through a line 36 and forced The suitably cooled po'rby means of a pump 3'7 through the, radiant coil 3 positioned in the furnace 1. The reflux condensate passing through the radiant coil 3 may be highly cracked under vapor phase cracking conditions which results in improved antiknock qualities. The highly crackedoil in vaporous form may then be passed through a transfer line 38 into the lower portion of the enlarged chambers 4 and 5 a by means of valved lines 39 and 41 respectively. The vapors within the enlarged chambers 4 and 5 may be digested therein under superatmospheric pressure for a period sufliciently long to accomplish the desired conversion thereof. Any

liquid constituents resulting from the digestion operation may be withdrawn through the outlets 42 and 43 at a rate adequate to prevent the accumulation of any liquidwithin either of the vessels. In order to equalize the temperature and pressure conditions existing within the vessels 4 and 5, a crossover line 44 may be provided. The vapors after being digested in the enlarged chamher 4 and 5 may be passed through lines 45 and 46 into a manifold line 47 connected to-the line 24 previously described. The pressure maintained on the enlarged vessels 4 and 5 may be substantially the same as that maintained on the enlarged vessel 7, or if desired thepressure may be lowered in thejchamber '7.

The highly heated vapors passing through the 5 line 4'7 and commingled with the vaporous and liquid constituents from the enlarged chamber 6 imparts additional heat to these constituents thereby providing for additional cracking thereof. The commingled vaporous and liquid constituents passing through the line 24 may then be introduced into the'lower portion of the enlarged chamber 7 and theoperation heretofore described carried out.

In operating in accordance with my invention, I

the enlarged chambers 4, 5 and 7 and the bubble tower 8 may be operated at substantially the same superatmospheric pressure whereas the chamber 6 that may be employed asa liquid phase soaking drum may be operated at a. higher I superatmospheric pressure. As an example, the former vessels may be operated at about 200 pounds per square inch and the latter vessel at about 400 pounds per. square inch. In the digestion of the fresh charge in the chamberB, I prefer in order to avoid detrimental coke too high temperature-liquidphase digestion. to maintain amoderate cracking temperature in excess of 800 F. and preferably in the order of 850 F. and which many case should be below 900 F. i e V m: a preferredr'method of operation in accordance with my invention, preheated to a temperature of about 500 F. in passing through the coil 15 and the heat exchanger 1'! and raised to a temperature of about 860 passed to the enlarged chamber 6 wherein it may be digested in the liquid phase. A sup'eratmospheric pressure of about 400 pounds may be maintained on theoil while passing through the heating coil and while being digested in the enlarged chamber 6.

The reflux condensate may be passed through the radiant coil 3 at a pressure of about 200 pounds per square inch and therein subjected to vapor phase cracking condiwhich may result from fresh charge may be.

F. in the convection coil 2. The oil may then be fromthe bubble tower 8 excellent anti-knock properties.'

enlarged chamber 7, cooling and condensation of the vapors and additional heating and vaporization of the fresh charge is efiected. The portion of the reflux condensate used as a cooling medium may be of a temperature of about 250 F. and may be introduced through the line 29 in order to provide the necessaryrefiuxin'g medium. The vapors resulting from the primary fractionating and evaporation operation may then be passed through the bubble tower 8 and the reflux condenser 9 at about 200 pounds per square inch pressure and therein fractionated to obtain a final vapor fraction having an end point at about 400 F. The vapor fraction may then be condensed in the condenser 11 and has been found to possess In operating in accordance with the conditions herein set forth, a gasoline distillate having an octane number of about 76 was recovered in the gasoline distillate receiver 12. I

Obviously many modifications may be made without departing from the spirit of the invention and therefore only such limitations are to be imposed on the scope thereof as are indicated in the appended claims.

What I claim is:

1. The process of cracking hydrocarbon oil that comprises subjecting a relatively clean cycle condensate to a cracking temperature in excess of 900" F. while being maintained under a superatmospheric pressure, subjecting a relatively dirty fresh charging stock to a cracking temperature of the order of 850 F. while being maintained under superatmospheric pressure, directing said highly heated condensate to an enlarged reaction chamber maintained at cracking temperature and under superatmospheric pressure, directing said heated iresh charging stock to a separate enlarged chamber maintained at crackingtemperature and under superatmospheric pressure, withdrawing liquid from said first reaction chamber to prevent the accumulation of liquid therein, passing vaporous constituents separated in both of said reaction chambers into another chamber, withdrawing liquid'from said second chamber and introducing it into said last mentioned chamber, and fractionating the resulting vaporous constituents to form the aforementioned clean-condensate. Y r

2. The process of cracking hydrocarbon oils that comprises subjecting a relatively clean cycle condensate to a cracking temperature under superatmospheric pressure to effect a high rate of cracking per pass, subjecting fresh charging stocktda cracking temperature under superatmospheric pressure under conditions to effect a lower rate of cracking per pass, directing said highly heated condensate to an enlarged reaction chamber maintained at cracking temperature under superatmospheric pressure, directing said heated fresh charging stock to a second enlarged chamber maintained at cracking temperature under superatmospheric pressure, withdrawing liquid from the first reaction chamber to prevent the accumulation of liquid therein while maintaining a substantial body of liquid oil undergoing cracking in the other reaction chamber, passing vaporous constituents separated in both of said reaction chambers into a primary fractionating zone, withdrawing liquid from said second reaction chamber and introducing it into said primary fractionating zone, subjecting the constituents introduced into said primary fractionating zone to fractionation therein to form a liquid fraction and a vapor fraction and subjecting said vapor fraction to'further fractionation to form the aforementioned clean condensate.

JOSEPH K. ROBERTS. 

